Workpieces which are thin or small often need to be fixed to a transferring belt to be washed or transferred. A packing machine is used to pack the workpiece in a feed tray. A conventional packing machine can include a cutting assembly, a vacuum-lifting assembly, and a packing assembly. The cutting assembly cuts the side of the transferring belt where it is connected with the workpiece, and separates the workpiece from the transferring belt. The lifting assembly lifts the workpiece by a vacuum pump, and transfers the workpiece to the packing assembly. The packing assembly packs the workpiece in the feed tray. It is difficult to accurately position the workpiece on the transferring belt before the cutting assembly. Thus, the cutting assembly cannot always with reliable precision separate the workpiece from the transferring belt. In addition, the lifting assembly can shift when attempting to lift the workpiece, air leaks between the vacuum-lifting assembly and the workpiece can sometimes cause further errors in the precise locating of the workpiece.